Field of the Invention
The invention relates to a music synthesizer.
Related Art
FIG. 21 is a block diagram showing a configuration of a conventional synthesizer. The synthesizer shown in FIG. 21 receives an input of a guitar sound or a microphone sound and thereby produces a synthesizer sound corresponding to the input sound. The synthesizer includes a pitch detector 211, a gate detector 212 and a waveform generating means 213.
The pitch detector 211 detects a frequency (pitch) of the input sound and outputs information (hereinafter “pitch information”) of the detected pitch. The gate detector 212 compares a signal level of the input sound with a predetermined threshold value and thereby detects presence or absence of the input sound. The gate detector 212 outputs gate-ON information when detecting the input sound, and outputs gate-OFF information when no longer detecting the input sound.
The waveform generating means 213 includes a sound source (sounding body) for producing the synthesizer sound. The waveform generating means 213 produces, as the synthesizer sound, sounds of various waveforms (e.g., sine wave, sawtooth wave and square wave, etc.) corresponding to parameters set by a parameter setting means (not illustrated).
When the gate-ON information is received from the gate detector 212, the waveform generating means 213 starts to produce the synthesizer sound, and during the production of the synthesizer sound, the waveform generating means 213 controls the frequency of the synthesizer sound to be a frequency corresponding to the pitch information received from the pitch detector 211. Then, when the gate-OFF information is received from the gate detector 212, the waveform generating means 213 muffles the synthesizer sound.
FIG. 22 is a block diagram showing a configuration of another conventional synthesizer. The synthesizer shown in FIG. 22 is, e.g., the synthesizer described in Patent Document 1 (JPH09-006351 A), so-called a polyphonic guitar synthesizer. This synthesizer is capable of producing a synthesizer sound individually not only when a single note is played but also when a plurality of strings are played at the same time (i.e., even when a chord is played).
As shown in FIG. 22, the synthesizer includes six strings 221 stretched on a guitar, a pickup 222, a pitch detector 223, a gate detector 224, a waveform generating means 225 and a mixer 226. The pickup 222 converts vibration of the string 221 into an electrical signal. The pickup 222 is independently provided for each of the six strings 221 and is capable of picking out the vibration of each string 221 as an electrical signal individually.
The pitch detector 223 is a detector similar to the pitch detector 211 and is provided corresponding to each of the six strings 221. The gate detector 224 is a detector similar to the gate detector 212 and is provided corresponding to each of the six strings 221. The waveform generating means 225 is a waveform generating means similar to the waveform generating means 213 and is provided corresponding to each of the six strings 221. The mixer 226 adds up outputs from each waveform generating means 225 corresponding to each string 221 and outputs a result thereof.
(1) Issue Relating to Timbre of Synthesizer Sound
In the aforementioned conventional synthesizer, whether the type of the input sound is a guitar sound or a microphone sound such as a singing voice, the pitch detector outputs one piece of pitch information for one input sound, and the waveform generating means outputs the synthesizer sound at a frequency corresponding to the pitch information. In other words, whether a guitar produces a sound having a pitch name “Do” or a singer sings a note having a pitch name “Do,” the pitch detector will detect the same pitch name “Do.” This means that a synthesizer sound outputted according to a detected pitch will have the same timbre regardless of the type of the input sound.
Therefore, although guitar sound and singing voice have completely different timbres, a synthesizer sound outputted for the same pitch name will have the same timbre without making use of the characteristics of the guitar sound or the singing voice. As a result, the timbre of the synthesizer sound becomes monotonous.
Moreover, the reason why timbre varies according to the type of sound such as guitar sound or singing voice is that harmonic components contained in that sound vary. A harmonic refers to a sound having a frequency that is an integral multiple of (e.g., twice, triple, etc.) the frequency of a fundamental pitch sound (hereinafter “fundamental tone”). According to how the harmonics are contained as components of a sound, characteristics are imparted to the timbre of that sound. The conventional synthesizer does not collect such timbre characteristics as information from the input sound, but merely acquires the information of one pitch as a representative value.
(2) Issue Relating to Gate Detection
In the conventional synthesizer, the gate detector is used to output the gate-ON information when the input sound is detected, and to output the gate-OFF information when the input sound is no longer detected. However, because level variation of an actual sound or voice is complicated, the gate detector sometimes performs detection different from that intended by the performer or the singer, i.e., erroneous detection.
FIG. 23 shows an example of erroneous detection performed by the gate detector. In the example shown in FIG. 23, an input sound 231 is inputted as a series of sounds (sounds that are continuous without being interrupted halfway). A broken line 232 indicates transition in level obtained from the input sound 231. The level of the input sound 231 is temporarily lower than a threshold value 233 at halfway time T1. The gate detector outputs the gate-OFF information as the level of the input sound 231 becomes lower than the threshold value 233.
Then, the level of the input sound 231 exceeds the threshold value 233 again at halfway time T2. Accordingly, the gate detector outputs the gate-ON information. As a result, the waveform generating means silences the synthesizer at time T1, and then resumes sound production at time T2. In other words, although the input sound 231 was inputted as a series of sounds, a synthesizer sound that is temporarily interrupted in the middle is produced. This is called erroneous detection in gate detection.
Regarding this, it may be considered to prevent the erroneous detection by reducing the threshold value. However, because of the reduction in the threshold value, the gate-OFF information and gate-ON information can be sensitively outputted even for a feeble signal. Accordingly, production of the synthesizer sound may even be initiated by, e.g., a noise-like signal. This is also erroneous detection in gate detection.
Alternatively, from the input sound, it may be considered to perform smoothing when acquiring the level of the input sound. In detail, in order to achieve a more gradual level variation, a moving average may be utilized, or a time constant that the level follows for an audio input is increased, so as to improve detection stability.
However, because of the more gradual level variation due to the smoothing, another problem occurs, namely, response in gate detection becomes poor. That is, time from input of a sound until output of the gate-ON information is increased. As for output of the gate-OFF information, the same problem occurs. The poor response in gate detection may cause poor response to a performance, and therefore becomes a main cause of an incompatible feeling for the performer.
In gate detection, in addition to the aforementioned erroneous detection problem, there is a problem that the synthesizer sound is monotonous. The synthesizer only starts sound production in response to the gate-ON information and is silenced in response to the gate-OFF information. As shown in FIG. 24A, the level of the produced synthesizer sound does not vary.
In contrast, as shown in FIG. 24B, at the start of production of the synthesizer sound, an envelope generator is used to control the level of the synthesizer sound according to a time-series level variation pattern (shown by the broken line 241) that was pre-programmed, thereby making it possible to obtain a synthesizer sound rich in level variation. However, the level variation controlled by the envelope generator has the same pattern for the gate-ON information every time. Hence, the synthesizer sound is even more monotonous in this respect.
(3) Issue Relating to Polyphonic Guitar Synthesizer
The aforementioned conventional polyphonic guitar synthesizer (in FIG. 22) includes the pitch detector 223, the gate detector 224, and the waveform generating means 225 of a plurality of systems in accordance with the number of strings stretched on the guitar. The configuration shown in FIG. 22 is specialized for an instrument called a six-string guitar, and enhancements will be necessary for adapting the configuration to guitars other than the six-string such as those with seven or eight strings. That is, since it is necessary to change the processing configuration (specifically, the numbers of the pitch detector, the gate detector and the waveform generating means) according to the number of strings, the polyphonic guitar synthesizer made for six-string guitars, for example, cannot be applied to the guitars other than the six-string without change.
In addition, according to various types of stringed instruments such as guitars or basses, it is necessary to change physical configuration (number of installation, or distance between pickups, etc.) of pickups. Therefore, in this respect, the polyphonic guitar synthesizer made for a certain type of stringed instrument cannot be applied to the other types of stringed instruments.